1. Field
The disclosed embodiments relate to a substrate transport apparatus and, more particularly, to substrate transport apparatus with multiple movable arms utilizing a mechanical switch mechanism.
2. Brief Description of Related Developments
In conventional multiple arm substrate transport apparatus, the arms or linkages of the transports are actuated by a complex arrangement of three or more motors, which for example may be configured in a coaxial manner and coupled to the linkages through concentrically arranged hollow shafts for providing the transport with movement having three degrees of freedom. Typically the outermost shaft may be coupled to a hub for rotating the multiple arms about, for example, a central axis of rotation. Two inner shafts, for example, may be connected to a respective one of the multiple arms through independent belt and pulley arrangements. As may be realized, the larger the number of motors employed for effecting movement of the transport, the greater the burden on the control system controlling the motion of the transport. Also, the larger number of motors employed increases the potential for motor failure as well as the cost of the transport.
The conventional multiple arm transport apparatus may be used in transport chambers or other substrate processing equipment where the transport apparatus and its drive system are located within and/or partially below the chamber/equipment so that the space available for other substrate processing components (e.g. vacuum pumps, etc.) is limited or otherwise constrained in some way. In conventional systems this may cause an increase in the size of the transport chamber to allow for mounting, for example, vacuum pumps at locations other than the bottom of the chamber/equipment. This results in incremental costs.
Conventional non-coaxial side-by-side dual SCARA (Selective Compliant Articulated Robot Arm) arms are offered for sale by several companies; the UTW and UTV series of robots by MECS Korea, Inc., the RR series of robots by Rorze Automation, Inc. and the LTHR, STHR and SPR series of robots by JEL Corp. An example of a side-by-side dual arm SCARA transfer device can be found in U.S. Pat. No. 5,765,444.
An exemplary configuration of a conventional non-coaxial side-by-side dual arm robot is shown in FIGS. 1 and 1A. The robot is built around a pivoting hub, which carries two SCARA arms or linkages. The left linkage has an upper arm, a forearm and an end effector coupled in series through revolute joints. A belt and pulley arrangement is used to constrain the motion of the left arm so that rotation of the upper arm with respect to the hub produces rotation of the forearm in the opposite direction (e.g. clockwise upper arm rotation causes counterclockwise forearm rotation). Another belt and pulley arrangement is used to maintain radial orientation of the end effector. The right linkage may be a mirror image of the left arm. The end effectors of the left and right arms move in different horizontal planes to allow for unrestricted motion of the two linkages of the robot. As can be seen in FIGS. 1B-1D, by rotating the left and right upper arms the respective linkages can be extended independently in a common radial direction with respect to the pivot point of the hub.
In the conventional side-by-side robots as shown in FIGS. 1, 1A-D, the robot arms or linkages are actuated by a complex arrangement of three (or more) motors, which for example may be configured in a coaxial manner, coupled to the robot through hollow shafts to provide the robot with movement having three degrees of freedom. The outermost shaft may be coupled to the hub, while the two inner shafts may be coupled to the upper arms of the left and right linkages through independent belt and pulley arrangements. As may be realized, the larger the number of motors employed for effecting movement of the robot arm, the greater the burden on the control system controlling robot motion. Also, the larger the number of motors employed increases the potential for motor failure as well as the cost of the robot.
The conventional side-by-side robots as shown in FIGS. 1A-D are used in transport chambers where the robot and drive section are located within the chamber so as to substantially prevent or at best encumber and limit the space envelope available for mounting of other components to the chamber such as atmosphere control systems (e.g. vacuum pumps to the bottom of the transport chamber). In conventional systems this may cause an increase in the size of the transport chamber for mounting of vacuum pumps at locations other than the bottom of the chamber. This results in incremental costs.
It would also be advantageous to have a robot manipulator with independently movable arms with reduced complexity, containment area and improved reliability and cleanliness of the robotic system.